Piston



Sept. 12, 1961 CORNET 2,999,727

PISTON Filed June 2, 1958 3 Sheets-Sheet l E/JM 11%,.

A. CORNET Sept. 12, 1961 PISTON 3 Sheets-Sheet 2 Filed June 2, 1958 AAmef Cam [r By M1 ATTX A. CORNET Sept. 12, 1961 PISTON 3 Sheets-Sheet 3 Filed June 2. 1958 p and;

nitd States. Pate This invention relates-to pistons for machines having pistonsin which the pistonsare subject to thermal and mechanical stresses.

All metals or alloys Which-are used for manufacturing pistons possess certain advantageous properties, and others that are disadvantageous, such that their choice is guided by the qualities'to' which is given preference. Steel, that is interestingbylowexpansion coeificient, its good friction qualities and" its resistance to wear, has often been preferred to light alloys, whose. correspond,- ing properties are however less favourable, but have the advantage of a much smaller specific weight and a very good thermal conductivity. But the pistons-of light alloy are relatively expensive, on the one hand because of the high price of the raw material, and on the other hand because of the exp'edientsof construction, destined to correct the effects of expansion, which complicate their manufacture.

In existing pistons, generally'manufactured by foundry casting, the thickness of the skirt in the proximity of the bosses of the gudgeon-pin is considerably reinforced. This results in an unequal distribution of the masses, and consequently of the rigidity of-the piston, as well as of the heating of the same, thus realizing four danger zones on one part of-theother of the two bosses. his in these zones of transition, between the reinforced and remaining parts of the skirt, that are greater in effect, the risks of the piston seizing under mechanical and thermal stresses and more particularly under the action of the forcesof rocking. Means utilized for reducing these risks of seizing consist of adopting oval shapes, of more or less complex profiles which complicate manufacture.

It is an object ofthis invention to provide an improved type of piston utilizing the advantages'of steel or similar metals.

It is another object of the'present invention to provide a pistonof simple and economic construction free from the above disadvantages and which, in view of itsmode of construction, assures a g'oodevacuation of heat from the head to the base ofvthe' skirt of the piston.

The piston according to the present invention, being adapted to be connected to'a connecting rod'by means of a'gudgeon-pin, is made of sheet metal, preferably sheet steel, in several parts assembled by welding with an interior stifl ening armature comprising at least a pair of plates: adapted to support a bearing of'said gudgeon-pin and connected to the head-ofthe piston on the one hand and to the skirt on the other hand.

Due to their welded contact with the head of the pistonv and the base of the skirt, the plates offer a' direct route of evacuation of heat by conductibility.

According to one embodiment of the invention the stiifening comprises two stamped plates welded together in the longitudinal plane of'the axis of the gudgeon-pin.

In another embodiment of the invention said plates are orientated perpendicularly to the axis of 'the gudgeonp'in and are therefore susceptible to give to the piston a greater rigidity'in the'sense' of rocking, and assuring, consequently an irrepr oachable guiding. In the case of such an orientation the expansion of the plates contributes furthermore to the improvement of the guiding which is efiected from a more favorable point of view.

This arrangement of interior stiffeningarmaturepen mits a distribution of the diverse eiforts on a larger part of the circumference and a consecutive reduction of the aluminium alloys, the respective values being 5 kg/rnm?v for aluminium alloys and 25' l g./mm.= for mild steel at ambienttemperature. The, difference is still much more favourable for the steel at operating temperatures of the piston, since at 300-- C. for example the resistance in question falls toless than 3 kg./mm. for alinninium alloys While rising'to 3i) lag/mm. for mild steels.

The invention will now be described with reference to the accompanying drawings which show three forms of embodiments of pistons according to the invention and in which:

FIGURE 1' shows a first embodiment in perspective view and cut along the longitudinal plane containing the axis of the gudgeon-pin;

FIGUREZ-is a front view of one of the pieces stamped in-the form of astirrup, constituting the stiffening armature and-the bosses of the gudgeon-pin;

FIGURE 3 i's-a view taken along line Iii-ill of FIG UR E 2;

FIGURE 4 is= aview similar to FIGURE 1 showing a second embodiment of the invention;

FIGURE 5 shows in perspective one of the pieces cone stituting the body of the piston in the embodiment according to FIGURE 4;

FIGURE 6 is an end View of the piece of FIG. 5 in one-stage of manufacture;

FIGURE 7 is a sectional elevational view of a piston according to a third embodiment, taken along the line VII-VII of FIGURE 8;

FIGURE 8 is a half-view, in plan taken along the line VlII-VIII of'F'IGURE 7;

FIGURE 9 is a partial view of the upper part of a variation in whichthe head and skirt portions of piston are formed in a single piece by stamping;

FIGURE 10 is a similar view of a second. variation of the upper part with an added cap formed with grooves;

FIGURE 11 is a similar view of a third variation having welded rings, and

FIGURE 12 is a similar view of a fourth variation with a mounted head portion.

In the embodiment according to FIGURE 1, the piston has a cylindrical body stamped in one piece, comprising a flat head 1, a lateral portion 2 adjacent said head and in which grooves 3 are formed by axial pressing and a cylindrical skirt 4'provided, along the axis of gudgeon-pin, with two opposed clearance holes 5.

The bosses of the gudgeon-pin are formed by two plates coupled in the longitudinal plane containing the axis of the gudgeon-pin (not shown). Each plate (FIG-i URES 2 and 3) isformed by a metal sheet 6 stamped out in the form of a stirrup. The cross-piece '7 is bordered exteriorly with a flange 8 placed at right-angle for fixing to the head 1' of the body of the piston, and has a length less than the diameter of the walls of the head and of the grooves for the rings. Branches 9 of the stirrup are formed with two coaxial semi-cylinders for mounting the gudgeon-pin, and extending beyond and laterally to each, formedby folding, is a tongue 11 for fixing to the skirt :of the.piston.. At the same time as the housings, a stifiening rib 12 of semi-circular section can be stamped Patented; Sept. 12, 119.51;

in the stirrup. The two plates are assembled face to face by welding; their assembly is fixed in the body of the piston by welding the flanges 8 to the interior face of the head 1 and the tonmies 11 to the internal wall of the skirt 4. Bushings (not shown) can be mounted in the bosses of the gudgeon-pin constituted by the assembled plates.

In this form of embodiment, a variation can consist of providing, during the axial stamping of the body of the piston, a head portion of reduced diameter, on which is mounted and fixed by welding a piece presenting the ring grooves eventually provided with a head, as is described hereinafter.

According to FIGURE 4, it is the body of the piston proper which is constituted by two stamped out shells, assembled face to face in the longitudinal plane of the piston comprising the axis of the gudgeon-pin.

Each shell is semi-cylindrical with a top portion 13 (FIGURES and 6). The portion 14 adjacent to this top portion is of a lesser diameter than that of the bottom of the grooves. It is connected by a shoulder 15 to the portion which forms the skirt 4 of the piston. The stamping of the blank (FIGURE 6) leaves on the periphery a broad border band or flange 16, which is folded in the diametral plane to form a band in which are pressed the housings for the gudgeon-pin. Beyond the shoulder 15 this flange 16 is separated from the part which forms the cylindrical skirt, and, when folded, an inwardly directed diagonal pleat 17 is formed in each corner of the top portion and of the cylindrical part 14; maintained by welding, it reinforces the radial peripheral stififening formed by the folded flange. In the portions 18 of flange 16 which are detached from the skirt 14 are stamped the coaxial semi-cylindrical housings '10 for the gudgeon-pin, corresponding clearance holes 5 being provided in the skirt 4. The extremities of the portions 18 can be fastened to the skirt by gussets of welded sheetmetal (not shown).

The two plates are assembled face to face by welding to constitute the piston (FIGURE 4). On the portion 14 is engaged as far as the shoulder 15, a sleeve 19, in which are cut the grooves 3, all being covered by a disk 20, forming the head proper of the piston, that is fixed by welding to the top portion 13. The sleeve '19 can be stamped from one piece with the head 20.

According to the embodiment shown in FIGURES 7 and 8, the piston comprises a skirt Zll constituted by a section of mild steel sheet tube having undergone a shrinkage in its upper part to form a neck 22; a throat 23 being arranged at the base of this neck to receive a keeper ring 24 of copper for brazing. Two diametrically opposed cylindrical bosses 25 are, moreover, stamped in the skirt to each receive the exterior extremity of a ring or sleeve 25 destined to form a bearing for a gudgeon-pin (not shown). c

The neck 22 is covered by a cap 28 forming the head of the piston with grooves 29, for the tightness rings, and 30 for the scraper ring. This cap, equally in sheet steel, is obtained by stamping followed by machining the grooves.

The piston according to this embodiment comprises finally two plates or partitions 31 of mild steel sheet stamped to the form shown; each of the plates is formed with a cylindrical boss 32. supporting at its internal extremity a corresponding bearing 26, and comprising an upper flange 33 disposed to contact the internal face of the head portion of the piston, and continuing on each side by lateral ribs 34 which follow in descending the neck 22 firstly, and th n the internal face of the said skirt proper, along most of the length of the latter,-on either side of each bearing 26. These plates comprise finally a certain number of perforations 35 designed to provide lightness.

The contact surfaces of these pieces, notably the internal surfaces of bosses 215, 32 and/or the exterior sure aaasnar A faces of bearings 26, the external surfaces of flanges 33 and 34 of plates 31, being previously covered with copper, the assembly is brazed in a kiln or furnace at a controlled atmosphere, in an atmosphere of hydrogen for example: in this manner there is elfected a rapid and solid welding of various assemblies, the assembly of pieces being carried in the kiln at a temperature higher than the melting point of copper.

Experience confirms that the behaviour of a piston thus constructed is remarkable in use and its guiding in the cylinder is irreproachable: examination of the external surface of the skirt, after prolonged operation, verifies the effect to the guiding orientated by the stifiening armature perpendicularly to the gudgeon-pin, in the most favourable manner, consequently, protecting the piston against the effects of rocking.

The piston according to the invention is subject to various forms of modification. 7

Thus, for example, as shown in FIGURE 9, skirt 40 and head portion carrying segments 41 can be made in a single piece by deep cylindrical stamping, the ring grooves being effected afterwards by embossing the body of the piston thus formed.

FIGURE 10 shows a second variation constituted by the association of a skirt 42, formed by double stamping, with a neck 43 closed by a top portion 44, this neck and top portion being doubled exteriorly by a ring carrying cap 45 effected by an embossing operation, die-stamping, or the like followed by the machining of the ring grooves. The cap forming the head is secured by welding around the neck 43 and above the top portion 44 of the skirt.

Furthermore, at the periphery of the head 45, directly above the ring grooves, can be arranged'a groove 55 adapted to receive a filling of sodium or any other material which will assure, by changing its state at the high functioning temperatures of this part of the piston, a thermal protection of the segments and principally the first segment. A similar arrangement can be equally provided for, if desired, in either forms of carrying out the invention. This means of thermal protection of the segments can be particularly utilized, for example, in the case of diesel motor pistons.

According to the variation of FIGURE 11, the cap has segments which are replaceable on a skirt, neck and top portion (42-43-44), of the same type as that of the preceding figure, by an external disc plate 46 and rings 47, 48 defining with'the peripheral part of said disc plate, and also with shoulder 49 of the skirt proper, the ringgrooves.

FIGURE 12 shows yet another variation in which the skirt 50 is a simple steel tube portion in one extremity of which is engaged, by a peripheral weld 51, a ring carrying cap 52; the ring grooves 53, 54 are machined in the cylindrical surface of this cap whereas the scraper-ring groove 55 has one of its sides constituted by the end edge of the skirt aligned with shoulder 56 arranged to this effect above the collar of fixation of the cap 52.

The process of manufacturing the pistons according to the invention comprises embossing the various parts of the piston, assembling said parts with the interposition of weld at their joints, the surfaces of the joints having been previously copper covered, particularly the joints of the stiffening armature, and heating the said piston assembly in a controlled neutral or reducing atmosphere (in hydrogen for example) to weld-braze the said joints thus giving a strong, rigid and reliable assembly. The assembling of parts is carried out in a kiln at a temperature higher than the melting point of copper. This controlled atmosphere effects a rapid weld-brazing with a corresponding perfect solidarity of the piston. The piston is thereafter rectified and electrolytically treated to assure the usual protection of the surfaces.

It will be understood it is not necessary that all the parts of the piston are realized in the same metal, therefore in the case of the variation of FIGURE 11 for example, the external disc plate 46, destined to contact directly the gases, can be made of diiferent metal from the other parts. The same thing applies to the bearing sleeves 26 (FIGURES 7 and 8).

I claim:

1. A piston formed of sheet metal, and comprising a skirt portion, a head portion having a head part and a grooved annular part, two sleeves forming bearings for a wrist pin, two armature plates orientated in a plane perpendicular to the axis of the wrist pin bearings, means for Welding said plates to said head part on the one hand and to a major portion of said skirt portion on the other hand and cylindrical openings formed in the skirt on the one hand, and in said armature plates on the other hand, to support the sleeves through a welded connection.

2. A piston as claimed in claim 1, wherein the skirt and head portions are formed in one piece.

3. A piston as claimed in claim 1, wherein an annular peripheral cavity arranged at the interior of the head portion is filled with a material the melting point of which is below the operating temperature of the piston.

4. A piston formed of sheet metal and comprising a skirt portion having an upper cylindrical part and a lower cylindrical part of increased diameter, a head portion having a head part and a grooved annular part, said grooved annular part being fitted onto said upper cylindrical part of said skirt portion, two coaxial cylindrical sleeves providing bearings for a wrist pin, two identical armature plates oriented perpendicularly to the axis of said sleeves, and cylindrical openings formed in said skirt portion on the one hand and in said armature plates on.

the other hand to support said sleeves through a welded connection, and means for welding said plates to said head part of said head portion on the one hand and to said lower cylindrical part of said skirt portion on the other hand.

5. A piston comprising a cylindrical skirt portion having two diametrically opposed and aligned holes, a head portion closing said skirt portion at one end, a pair of wrist pin bosses respectively aligned with said diametrically opposed holes, and two internal partition plates, one for each boss, positioned transversely of the Wrist pin bosses and provided with holes aligned with the holes in the skirt portion to support together with said skirt portion said bosses and extending from means connecting said partition plates with said head portion, on the one hand, to means connecting said partition plates along a major portion of the internal surface of said skirt portion in a zone thereof which is, with respect to said bosses, at the opposite of said head portion.

6. A piston as claimed in claim 5, wherein said partition plates are orientated in a plane perpendicular to the wrist pin boss axis and having an upper connection with the internal face of said head portion and two lateral connections with the internal surface of said skint portion, said lateral connections extending on either side of said boss along a substantial part of the length of said skirt portion.

7. A piston formed of sheet metal and comprising a head portion and a skint portion, said head portion comprising a bottom part and a grooved annular part, an interior stiifening armature, a wrist pin bearing supported by said stiffening armature, said armature being welded to said bottom part on the one hand and to a major portion of said skirt portion on the other hand, and comprising at least a pair of plates orientated perpendicularly to the axis of the wrist pin bearing which is supported by said stiffening armature and by said skirt portion.

8. A piston as claimed in claim 7, wherein an annular peripheral cavity provided at the interior of the head portion is filled with a material, the melting point of which is below the operating temperature of the piston.

9. A piston comprising a cylindrical skirt portion, a top portion closing said skirt portion at one end, a pair of wrist or gudgeon pin bosses respectively facing and aligned with two diametrically opposed lateral openings provided in said skirt portion, and at least one internal partition means serving to give rigidity to said piston and to support said bosses comprising a substantially straight and plane partition positioned transversely to the gudgeon pin axis and having an upper connection to the inner face of said top portion and two lateral connections with the inner face of said skirt portion, said lateral connections extending along a major portion of said skirt portion and below said gudgeon pin axis.

References Cited in the file of this patent UNITED STATES PATENTS 1,512,718 Soulis Oct, 21, 1924 1,790,664 Horton Feb. 3, 1931 2,044,379 Brennan June 16, 1936 2,174,644 Weatherhead et al. Oct. 3, 1939 2,315,403 Dillon Mar. 30, 1943 2,341,836 Wood Feb. 15, 1944 2,494,748 Ernestus Jan. 17, 1950 2,752,213 Swart et a1. June 26, 1956 2,855,253 Ayling Nov. 7, 1958 FOREIGN PATENTS 822,922 Germany Nov. 29, 1951 932,208 Germany Aug. 25, 1955 

